Traveling wave tube mixing apparatus



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Oct. 27, 1953 K. s. KNoL ETAL 2,657,305

TRAVELING WAVE TUBE MIXING APPARATUS Filed Jan. 16, 1948 K-s. KNoLaAA/ANDERzlEL x19 lNvENToRs .4, AGENT N :l v Le? Patented Oct. 27, 1953TRAVELING WAVE TUBE DIIXING APPARATUS Kornelis Swier Knol and Aldert vander Ziel, Eindhoven, Netherlands, assignors to Hartford National Bankand Trust Company, Hartford,

Conn., as trustee Application January 16, 1948, Serial N o. 2,767 IntheNetherlands January 28, 1947 (Cl. Z50-20) 9 Claims. 1

This invention relates to a mixer circuit-arrangement for centimetrewaves, in which use yis made of a so-called travelling wave amplifyingtube. A known construction of such atube used for the amplification ofcentimetre waves comprises a system for producing an electron beam, andin addition a helical conductor along which the waves to be amplifiedpropagate and which is arranged with respect to the said system in suchmanner that the electrons of the beam move approximately axially withthe helix. The waves to be amplified are fed to that end of the helixwhich is nearest to the electron beam, and the winding pitch of thehelix and/or the diameter; the turns and the voltages used for producingthe electron-beam are chosen to vbe such that the speed of propagationof the waves measured along the axis of the helix is slightly lower thanthe mean velocity of the electrons of the beam.

Under these conditions the electrons give off energy to the waves, sothat these amplied waves can be taken from the end of the helix remotefrom the source of electrons.

The invention is based on the recognition that a tube operating on thisprinciple may be used with a given modication, as a mixer tube forcentimetre waves.

For this purpose the oscillations to be mixed and an auxiliaryoscillation are fed, according to the invention, to the helicalconductor in such manner as to produce travelling waves along the helix(helices), these waves moving in the same sense, and preferably at thesame velocity or at a slightly lower velocity than the electrons. Afterhaving traversed the helix or helices the electrons are separatedaccording to their velocity with the aid of a suitable electrode systemfrom which at the same time the intermediate frequency oscillation istaken. l

The actual occurrence of an intermediate fre- 'quency oscillation in theoutput circuit is due to the fact that on traversing the helix orhelices the electrons of the beam reach different velocities owing tothe traversing waves, so that after velocity detection in the saidelectrode-system' Van oscillation of difference-frequency results in theoutput circuit.

The oscillation to be mixed and the auxiliary oscillation may jointly besupplied to the end of the same helix nearest to the source of elec- 2to avoid radiation of oscillations of the frequency of the auxiliaryoscillation by avoiding an aerial connected, if any, to the inputcircuit, the helix to which the oscillation to be mixed is supplied ispreferably located nearer to the source of electrons than the helix towhich the auxiliary oscillations are fed. Ii desired, the auxiliaryoscillation may be produced in the tube itself.

In the drawing,

Figure -1 is a schematic diagram of a iirst preferred embodiment of theinvention;

Fig. 2 is a curve explanatory rof the operation of Fig. 1; and

Fig. 3 is a schematic diagram of a second embodiment oi the invention.

In order that the invention may be more clearly understood and readilycarried into effect, it will now be described more fully with referenceto the accompanying drawing, in'whlch one enibodiment comprising twohelices is represented by way of example in Fig. l. The tube lrepresented therein comprises a system 2 for producing anelectron-beam,two helices il] and H ary ranged coaxially with the tube and Vin linewith one another and a system for velocity detection which consists of acylindrical electrode 3 and a collecting electrode 4 arranged slightlyobliquely relatively to the axis of the tube. In this case it isadvantageous to apply to the cylindrical electrode 3 a voltage slightlydiffering from earth potential and to apply a slightly positive voltageto the electrode fi. For the sake of simplicity the sources of potentialrequired for this purpose are not represented. The end of the helix IBlocated on the side of the source of electrons is earthed through animpedance E at which the input oscillations occurring at the terminalsl2 appear. The other end of this helix is earthed through an impedanceE, the Value of which substantially corresponds with the surge impedanceof the helixv ID, so that travelling waves moving from the left to theright occur therein. The source 'l for the auxiliary oscillation isconnected in between the left-hand end of the helix il and earth, whilstthe other end of this helix is likewise earthed through an impedance 8,the value of which is adapted to the helix Il, so that in the helix Iltravelling waves of the auxiliary frequency occur which move from theleft to As indicated by a dotted cylinder 3.

The operation of the circuit-arrangement may be described with referenceto Fig. 2. This figure shows a curve representing the relation betweenthe current I4 flowing from the electrode 4 to the output circuit andthe velocity of the electrons of the beam. According as this velocity islower more electrons of the beam will be attracted by the cylinder 3, sothat a smaller part will flow to the electrode li. Since the relationbetween the output current and the electron velocity is not linear, theelectrode system 3, 4 will operate as a velocity detector. Owing to thehelices it and ll the successive electrons of the beam reach differentvelocities in accordance with the intensity of the waves on the helicesI9 and l l, so that in the output circuit 9 an oscillation may occur,the frequency oi which is equal to the difference between thefrequencies of the 1oscillation to be mixed and the auxiliaryoscillaion.

Fig. 3 schematically illustrates a mixing ciicuit wherein the travelingwave tube includes but a single section helix I3, the local oscillationsl and the input oscillations both being applied to the terminus of thehelix adjacent the electron gun.

What we claim is:

1. Apparatus for mixing first and second highfrequency oscillations ofdifferent frequency to produce intermediate-frequency oscillationscomprising a traveling-wave electron beam tube including a helicalconductor for guiding oscillations, an electron beam source adjacent oneend of said conductor and a collector electrode adiacent the other endof said conductor, said source being arranged to direct an electron beamalong the axis of said helical conductor toward said collector electrodewith a velocity which at any point thereon exceeds that of the travelingwave of oscillations as measured along said axis, means to apply saidrst and second oscillations to said helical conductor to producetraveling waves thereon which advance in the same direction as saidelectron beam, and means to derive the intermediate-frequencyoscillations from said collector electrode.

2. Apparatus for mixing first and second highfrequency oscillations ofdifferent frequency to produce intermediate-frequency oscillationscomprising a traveling-wave electron beam tube including a helicalconductor for guiding oscillations, an electron beam gun adjacent oneend of said conductor and a collector electrode adjacent the other endof said conductor, said gun ybeing arranged to direct an electron beamalong the axis of sai-d helical conductor towards said collectorelectrode with a velocity which at any point thereon exceeds that of thetraveling wave of oscillations as measured along said axis, inputcircuit means to apply said first and second oscillations to saidhelical conductor at said one end thereof to produce a traveling wavethereon which advances in the same direction as said yelectron beam, animpedance connected to said other 4end of said conductor and having avalue matching the surge impedance of said conductor, and output circuitmeans to derive the intermediate-frequency oscillations from saidcollector electrode.

3. Apparatus for mixing first and second high frequency oscillations ofdifferent frequency to .produce intermediate-frequency oscillationscomprising a traveling wave electron beam tube including a helicalconductor for guiding oscillations, an electron beam gun adjacent oneend of said conductor, a collector electrode adjacent the other end ofsaid conductor and a retarding tubular electrode interposed between saidcollector electrode and the other end of said tube, said gun beingarranged to direct an electron beam along the axis of said helicalconductor through said tubular electrode towards said collectorelectrode with a velocity which at any point thereon exceeds that of thetraveling wave ofthe oscillations as measured along said axis, inputcircuit means to apply said first and second oscillations to saidhelical conductor at said one end thereof to produce a traveling wavethereon which advances in the same direction as said electron beam, animpedance connected to said other end of said conductor and having avalue matching the impedance of said conductor, and output circuit meansto derive the intermediatefrequency oscillations from said collectorelectrode, said last named means including a resonant circuit connectedbetween the collector electrode and said tubular electrode and tuned tosaid intermediate frequency.

4. An apparatus, as set forth in claim 3, further including means tobias said collector electrode positively with respect to said retardingelectrode.

5. An apparatus, as set forth in claim 3, wherein said collectorelectrode is disposed obliquely relative to the axis of said beam.

-6. Apparatus for mixing rst and second highfrequency oscillations ofdifferent frequency to produce intermediate-frequency oscillationscomprising a traveling-wave electron beam tube including a helicalconductor for guiding oscillations, said helical conductor beingconstituted by separate first and second sections each having endterminals, an electron beam gun adjacent one end of said helicalconductor., a collector electrode adjacent the other end of saidconductor, said gun being arranged to direct an electron beam along theaxis of said helical conductor successively through the first and secondsections thereof toward said collector electrode with a velocity whichat any point thereon exceeds that of the traveling wave of oscillationsas measured along said axis, means to apply said first oscillations tothe terminus of said first section adjacent said gun, means to applysaid second oscillations to the terminus of said second section adjacentsaid gun, and means to derive the intermediate-frequency oscillationsfrom said collector electrode.

'7. Apparatus for mixing first and second highfrequency oscillations ofdifferent frequency to produce intermediate-frequency oscillationscomprising a traveling wave electron beam tube including a helicalconductor for guiding oscillations, said helical conductor beingconstituted by separate first and second sections, an electron beam gunadjacent one end of said conductor, a collector electrode adjacent theother end of said conductor and a retarding tubular electrode interposedbetween said collector electrode and said other end of said conductor,said gun being arranged to direct an electron beam along the axis ofsaid helical conductor successively through the first and secondsections thereo toward said collector electrode with a velocity which atany point thereon `exceeds that of the traveling wave of oscillations asmeasured along said axis, nrst input circuit means to apply said nrstoscillations to the terminus of said `iirst ysection adjacent said gun,second input circuit 'means to apply said second oscillations to theterminus' of said second section adjacent said gun, and output circuitmeans to derive the intermediate-frequency oscillations from saidcollector electrode, said last named means including a resonant circuitconnected between the collector electrode and said tubular electrodean-d tuned to said intermediate frequency.

8. Apparatus for mixing first and second highfrequency oscillations toproduce intermediatefrequency oscillations, the frequency of said firstoscillations being high relative to said second oscillations, saidapparatus comprising a traveling wave electron beam including a helicalconductor for guiding oscillations, said helical conductor beingconstituted by separate rst and second sections, an electron beam gunadjacent one end of said conductor, a collector electrode adjacent theother end of said conductor and a retarding tubular electrode interposedbetween said collector electrode and said other end of said conductor,said gun being arranged to -direct an electron beam along the axis ofsaid helical conductor successively through the first and secondsections thereof toward said collector electrode with a velocity whichat any point thereon exceeds that of the traveling Wave of oscillationsas measured along said axis, rst input circuit means to apply said rstoscillations to the terminus of said rst section adjacent said gun, arst matching impedance connected to the other terminus of said rstsection, second input circuit means to apply said second oscillations tothe terminus of said second section adjacent said gun, a second matchingimpedance connected to the other terminus of said second section, andmeans to de- 6 rive the intermediate-frequency oscillations from saidcollector electrode, said last named means including a resonant circuittuned to the frequency of said intermediate frequency oscillations an-dconnected between saidvretarding and collector electrodes.

9. Mixing apparatus, as set forth in claim 8, wherein said collectorelectrode is disposed obliquely with respect to the axis of said beamand further including means to apply a constant voltage to saidcollector electrode which is positive with respect to said retardingelectrode.

KORNELIS SWIER KNOL. ALBERT VAN DER ZEL.

References Cited in the lle of this patent UNITED STATES PATENTS NumberName Date 2,064,469 Haeff Dec. 15, 1936 2,233,126 Haeff Feb. 25, 19412,289,756 Clavier et al. July 14, 1942 2,300,052 Lindenblad Oct. 27,1942 2,367,295 Llewellyn Jan. 16, 1945 2,508,228 Coeterier May 16, 19502,541,843 Tiley Feb. 13, 1951 2,575,383 Field Nov. 20, 1951 2,578,434Lindenblad Dec. 1l, 1951 2,580,007 Dohler et al Dec. 25, 1951 OTHERREFERENCES Article by Pierce and Field. pp. 108-111, Proc. of I. R. E.for Feb. 1947, vol. No. 35, No. 2. Copy in U. S. Patent Office,Scientific Library.

